Fiber optic router LOS light is on red

LOS means the fiber signal is not reaching the ONT/router properly. When it's green and steady, everything is fine. However, when it blinks red or stays solid red, it signifies a Loss of Signal, a problem preventing your router from communicating. A red LOS (Loss of Signal) light on your router or ONT usually indicates that the device is not receiving an optical signal from the fiber network. In many cases, the issue is temporary and can be fixed with a few basic checks before you call support. But the answer is still. How to fix a Red LOS Light on your WiFi Router? To fix a red LOS light on the router: Start by checking that the fiber or WAN cable is firmly connected and undamaged (no sharp bends or crushing), then clean the fiber connector if it looks dusty. [pdf]